1. Field of the Invention
The present invention relates to the preparation of optical fibers, and in particular to a method and apparatus for cleaning and/or stripping an optical fiber using a continuous or pulsed electrical arc.
2. Description of the Prior Art
Fiber optic cables are widely used in modern optical devices and optical communications systems. Optical fibers are strands of glass fiber processed so that light beams transmitted through the glass fiber are subject to total internal reflection wherein a large fraction of the incident intensity of light directed into the fiber is received at the other end of the fiber. In addition, a number of individual optical fibers may be grouped together to form what is known as a ribbon fiber.
For some applications, the optical fiber or fibers must be many kilometers long. It is therefore often necessary to splice two shorter lengths of optical fiber (a single fiber or a ribbon fiber) together to form a longer optical fiber. The need to splice optical fibers also arises when it is necessary to use a length longer than can be made from single preform, when an existing length of fiber breaks, or when apparatus such as an amplifier is to be incorporated into a length of fiber.
Optical fibers are usually coated with one or more protective layers, for example a polymer coating made of acrylate or polyimide, in order to protect the surface of the fiber from chemical or mechanical damage. In order to prepare the fibers to be cleaved and spliced, or in order to further process the fibers to manufacture optical devices such as optical sensors and other optical communications network components, it is necessary to remove the protective coating or coatings, a process known as stripping, and to clean the optical fiber to remove any remaining coating debris.
Conventional stripping methods include mechanical stripping, chemical stripping, and thermal stripping. Mechanical stripping typically involves a stripping tool, similar to a wire stripper, which cuts through the coating and scrapes it off. Mechanical stripping may result in nicks or scratches on the glass fiber surface, which could lead to cracks and degradation in the tensile strength of the fiber. Chemical stripping uses solvents or concentrated acids to remove the polymer coating. Chemical stripping is typically very costly, presents safety concerns due to the nature of the chemicals that are used, and, in some cases, may adversely affect the splice strength.
Moreover, conventional cleaning methods include chemical cleaning and electrical arc based cleaning. For example, prior art fusion splicing devices have typically cleaned optical fibers prior to splicing in two steps. In a first step, a chemical, typically alcohol, is used to remove large debris (large coating particles) from the cleaved end of the optical fiber that is left behind following the stripping step. Then, in a second step, a single electrical arc pulse, commonly referred to as a “prefuse arc,” is used to remove any small debris (smaller coating particles) that may remain after the chemical cleaning step. In particular, in this second step, the “prefuse arc” generates a plasma, and the cleaved end of the fiber is inserted into the plasma. The intense heat of the plasma vaporizes the remaining small debris. The prior, extra chemical cleaning step is necessary because using the “prefuse arc” and resulting plasma to remove large debris would result in the contamination of the electrodes, v-grooves and optics of the fusion splicer due to the sputtering of the large debris.
Thus, there is a need for an improved method of stripping and/or cleaning an optical fiber prior to splicing and/or cleaving steps.